Basement Flooding Prevention

Basement Flooding can happen in any home. The good news? You can take steps to  reduce the risk or prevent it from happening.

Causes of basement flooding

Causes of basement flooding can range from drainage issues to extreme weather events. Here are some common ways that a heavy downpour can make its way into your home:

Poor lot grading
All homes need to have the lot grading slope away from the structure to reduce the risk of basement flooding. If stormwater drains towards your home, it may seep down the foundation wall and gain entry. In fact, improper grading on your property can also negatively impact your neighbour’s property. Visit our Site Alteration page for more information.
Poor basement sealing
When a home is being built, the basement tiles and foundation need to be sealed properly. If this is not done correctly or deteriorates over time, water can begin to seep into the basement from the ground.
Weeping tile failure
Every home should have a weeping tile or foundation drain system built around the structure to help ensure that water doesn’t seep into the home. If this system has been installed incorrectly or fails, the basement may experience flooding, especially during heavy rains.
Improperly installed downspouts
Your downspout is intended to direct water away from your home and its foundation. Downspouts should be at least 1.5 to 2 metres (5 to 6 feet) away from the basement wall and drain away from the home, usually towards the street or backyard. If your downspouts are broken or missing, water could will pool next to the house where it can seep down the foundation wall and pour in through cracks in the foundation. If downspouts are connected to sewer (sometimes found in older homes), rainwater can contribute to overfilling sewer pipes causing them to backup into homes. If you have downspouts connected to sewer, they should be disconnected for discharge to your property as described above.
Eavestrough debris

Eavestroughs or roof gutters or are essential to moving water away from your home to keep your basement dry. Gutters clogged with leaves, twigs, seed pods and other debris stop water from moving off the roof, through the downspout and away from the home. Overflowing gutters will force water down the sides of the home where it can pool and seep into the basement.

Protecting your home before extreme weather events

Disasters happen but there are things you can do to reduce the risk that your home will be damaged. 

flood prevention diagram

Residential overland flooding is generally not covered by standard property insurance. Talk to your insurer about the types of water damage that are covered by your policy. The Intact Centre for Climate Adaptation is a helpful resource with some cost-effective tips for basement flood protection.

Here are some steps you can take to help reduce or prevent basement flooding from happening:

Inside your home
  • Maintain your plumbing system
  • Never flush wipes, or pour fats, or oils down your drain - they make clogs and cause backups!
  • Consider installing a backwater valve to prevent sewer lines from backing up in your home
  • If your floors are below ground level, install and maintain a sump pump system
Outside your home
  • Keep storm sewer grates on your curb clear of leaves, garbage, snow and ice
  • When landscaping, ensure the grading around your home slopes away from the foundation to help drain water away from your home 
  • Extend downspouts at least 2 meters away from foundations and use rain barrels
  • Clean and maintain eavestroughs and downspouts annually

  • If possible, build rain gardens and plant trees to increase rainwater infiltration

Here are some steps you can take if  your basement is flooding:

What to do if your home is flooding
  • Contact your home insurance company as soon as possible and take photos and videos of the damage for insurance claims.
  • Take precautions: do not enter rooms (e.g. basements) where the flood water has risen above outlets, baseboard heaters, or your furnace; power cords; or is near the electrical panel. Contact your hydro company immediately if this has occurred.
  • If you suspect sewer backups, report the flooding to Customer Service at 519-759-4150.
  • If you have experienced a sewer backup or if your backwater valve has been activated, do not use water for activities such as laundry or dishes, as this could lead to water ending up in your basement.
  • While cleaning up and following the steps listed above, it's important to wear steel-toed boots, sturdy work gloves, an N95 mask, and eye protection. This will help protect you from any unseen hazardous objects in the water. Make sure to follow the recommended cleanup procedures from the Government of Canada.
What to do after your home floods
  • When restoring your home to good order, consider wearing steel-toed boots, work gloves, an N95 mask, and eye protection to safeguard yourself against unseen hazardous objects under the water.
  • Prepare your home for potential heavy rain in the future.

Emergency preparedness 

Emergencies happen when we don’t expect them. Learn how to be emergency ready, and what to do during and after an emergency by visiting our Emergency Preparedness page.